"Scalable" here means extendibility, that is, the ability to be increased or decreased. For example, it indicates technological flexibility for handling many files, many users, and a wide variety of applications. Moreover, "tracking" conveys the meaning of following actions or behavior. For example, it is a means of tracking site-visit records of users on the internet by using Web cookies. In the case of scalable tracking, the meaning amounts to highly extendible tracking technology that uses various methods in conjunction to track the behavior of users.
